[BCK-518] Add edge statistics to graphMetadata (currently missing)

Priority: High Effort: 6 Type: Feature

The graphMetadata object is currently missing edge statistics. This needs to be added to provide complete graph information to clients.

Asana Task: https://app.asana.com/1/1206648675960041/project/1208204369345947/task/1210636930312409 BCK ID: BCK-518

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Migrated from Asana